> Authorities reportedly believe the smuggler went to the lengths he did in an effort to avoid Japan’s 10-percent import tariff.

To my understanding, when selling in Japan, the smugglers will need to either declare the capital gain tax, or sell it (at some) the black market heavily discounted.

When determining the capital gain tax, if no purchase receipt (=purchase price) can be provided, the purchase price is set at 10% of the current market value, leading to a big capital gain tax.

In any case it will be difficult for the smuggler to make up the savings of the 10% import tariff.

To my understanding, that 10% tariff is actually an added 10% consumption tax, which can be claimed back when transporting gold out of Japan.